A fabric is conventionally dried by continuously conveying a length through a drying chamber with the fabric supported in a manner providing a series of spaced and substantially parallel courses. Dryers of this type are commonly known as tenter dryers and each is provided with a first and second series of rollers, one series at each end of the chamber and arranged to enable a predetermined number of such courses to be established. Such dryers also have means to effect the advance of the fabric through the dryer at selected rates of travel and means to circulate the air through the chamber in direct contact with both surfaces of or through the fabric in adjacent courses and to heat the circulating air in a manner such that air withdrawn from the chamber is brought back to a selected temperature before again being forced back thereto. Among the advantages of such dryers is that they occupy relatively small areas as compared to that required for dryers of other types.
In the use of a dryer of the tenter type, a problem exists when a fabric, which term, as used throughout the application includes the finish thereof, may be damaged by air heated to a temperature to which other fabrics may be safely subjected. As long as free surface moisture is present to be evaporated from such a fabric, the temperature of the circulating air is not a problem. When the surfaces of the fabric dry as the fabric is advanced theough the chamber, the temperature of the fabric quickly responds to that of the circulating air so that in the exiting course or in a course or courses adjacent thereto, there is the certainty of damage to fabrics that cannot withstand such heating.
As the fabric in all courses are subject to air at approximately the same temperature, the drying of such fabrics has required that the temperature of the circulating air be reduced to an appropriate extent and also that the rate at which the fabric is passed through the chamber be reduced to an extent ensuring the drying of the fabric to the desired moisture content at the lowered temperature with the result that an objectionable but unavoidable time limitation is placed on production.